John Nichols writes about politics for The Nation magazine as its Washington correspondent.

Barack Obama beat Mitt Romney by a landslide Tuesday in the battleground state of Pennsylvania.

Romney grabbed the headlines Tuesday night, after winning the high-profile Pennsylvania Republican primary and four other northeastern-state GOP contests. With his main rival, Rick Santorum, out of the running, Romney finally started securing majorities — after four months of strugglng to get to the 50 percent mark. But the Republicn frontrunner who can't quite buy the love of his party was still losing more than 40 percent of the Pennsylvania GOP vote to Santorum's non-candidacy and the bitter-ender runs of Newt Gingrich and Ron Paul.

And while the attention was on Romney's "win," the numbers from Pennsylvania revealed that he was losing — by a whole lot — to Obama.

Obama was always going to prevail in Pennsylvania's Democratic primary, just as he has in every primary and caucus during the course of an election year where the president has been spared the inside-the-party wrangling that tripped up Lyndon Johnson in 1968, Jimmy Carter in 1980 and George H. W. Bush in 1992. According to the Associated Press count, Tuesday night's primaries in Pennsylvania and Rhode Island gave the president the last delegates he'll need to officially clinch the Democratic nomination.

Even as he went into Tuesday's primaries in a region where he should be strongest, and where he faces little organized opposition, Romney had to run hard, hoping to finish off former House Speaker Gingrich (who mounted a last-ditch drive in Delaware) and to avert any protest vote from diehard Santorum backers on the former senator's home turf.

Romney's worked hardest in Pennsylvania, bringing in Florida Senator Marco Rubio for a vice presidential test drive, making nine major stops and gathering with grassroots Republicans at a backyard picnic table where he famously dissed cookies from Allegheny County's popular Bethel Bakery. But even as Romney "swept" Pennsylvania, Delaware, New York, Connecticut and Rhode Island tonight, he was not winning enough delegates to claim the GOP nod.

The enthusiasm gap that has plagued Romney from the start of the race continues to be a frustration for the candidate who has bought his way into contention — boosted by his post–Citizens United Super PAC. With Santorum out, Gingrich edging toward the sidelines and Ron Paul campaigning part-time, Romney is doing everything he can to assume his role as the Republican challenger to the president. But it is not an easy fit; the new Gallup tracking poll has Obama opening up a 49–42 lead over Romney — numbers that suggest Mitt is still struggling to get the GOP base excited about a candidate they did not choose.

Nothing illustrates Romney's inability to energize the base quite so completely as the fact that — though it has been little noted by media that pay scant attention to the Democratic primaries — Romney has already "lost" quite a few contests with Barack Obama.

No, they are not listed on the same ballot, yet.

But in many of the states that have held primaries so far, there have been head-to-head Republican and Democratic races. Though the energy and attention has all been on the Republican side, Obama has quietly run up higher primary vote totals in a number of states — including Louisiana, Maryland, Missouri, Ohio, Vermont and the District of Columbia. In some blue states, such as Maryland, Obama got more votes than all the Republican candidates combined.

Of course, there are always local factors and complications, open and closed primary considerations, down-ballot races that draw voters. But the fact is that, in battleground states such as Missouri and Ohio, Obama has outpolled Romney. And in other battleground states, such as Wisconsin, he has come close to doing so — despite the fact that primary voters are often surprised to learn they have the option of casting a Democratic presidential ballot.

The pattern continued Tuesday night, with Obama sweeping past Romney in another battleground state: Pennsylvania.

The numbers — as opposed to the headlines — tell the real story.

They remind us that — "at the doorstep of the general election," as Obama spokesman Ben LaBolt refers to the moment — Mitt Romney is still unable to unite his own party. And,key states such as Missouri, Ohio and, now, Pennsylvania, he can't even keep pace with Barack Obama's primary vote totals.